From a623f12e303df7a24c52d58dec25847b83f137ee Mon Sep 17 00:00:00 2001
From: wnhlee <2wheeh@gmail.com>
Date: Tue, 30 Apr 2024 18:05:55 +0900
Subject: [PATCH] feat: implement useStickyIOS hook

---
 ui/src/app/(board)/review/write/page.tsx |  1 +
 ui/src/hooks/common/use-sticky-ios.ts    | 89 ++++++++++++++++++++++++
 ui/tailwind.config.ts                    |  5 ++
 3 files changed, 95 insertions(+)
 create mode 100644 ui/src/hooks/common/use-sticky-ios.ts

diff --git a/ui/src/app/(board)/review/write/page.tsx b/ui/src/app/(board)/review/write/page.tsx
index 0e124111..ff1154c1 100644
--- a/ui/src/app/(board)/review/write/page.tsx
+++ b/ui/src/app/(board)/review/write/page.tsx
@@ -10,6 +10,7 @@ import ReviewTitle from '@/components/review/client/review-title';
 
 import { EditorRefProvider } from '@/context/editor/editor-ref-context';
 import { ReviewProvider } from '@/context/review/review-context';
+
 import { MAX_CONTENT_LENGTH } from '@/lib/constants/review';
 
 const Editor = dynamic(() => import('@/editor'), {
diff --git a/ui/src/hooks/common/use-sticky-ios.ts b/ui/src/hooks/common/use-sticky-ios.ts
new file mode 100644
index 00000000..0f8e5417
--- /dev/null
+++ b/ui/src/hooks/common/use-sticky-ios.ts
@@ -0,0 +1,89 @@
+// This is a custom hook to fix the issue with sticky and the soft keyboard on ios.
+// on ios, when the soft keyboard is open, the keyboard pushes the content up.
+// This ends up getting the sticky element out of the screen.
+// As a workaround, we wrap the sticky element with a wrapper,
+// set a margin to the sticky element as much as the wrapper is out of the screen.
+import { useDebouncedCallback } from './use-debounced-callback';
+import { useCallback, useEffect, useRef } from 'react';
+
+const DEBOUNCE_TIME = 150; // ms
+const TRANSITION_CLASS = 'animate-slide-down';
+
+export function useStickyIOS<
+  StickyElementType extends HTMLElement = HTMLDivElement,
+  WrapperElementType extends HTMLElement = HTMLDivElement,
+>() {
+  const stickyRef = useRef<StickyElementType>(null);
+  const wrapperRef = useRef<WrapperElementType>(null);
+  const blurred = useRef(false);
+
+  const stickyOffsetRef = useRef(0);
+
+  const setMargin = () => {
+    const wrapper = wrapperRef.current;
+    const sticky = stickyRef.current;
+
+    if (!wrapper || !sticky) {
+      return;
+    }
+
+    const newPosition = wrapper.getBoundingClientRect().top;
+    // do nothing if wrapper remains in the screen
+    if (newPosition >= 0) {
+      return;
+    }
+
+    stickyRef.current.classList.add(TRANSITION_CLASS);
+    // if wrapper is out of the screen,
+    // add a margin to show the sticky element
+    stickyOffsetRef.current = Math.abs(newPosition);
+
+    // set the margin by the new fixed position
+    sticky.style.marginTop = `${stickyOffsetRef.current}px`;
+  };
+
+  const debouncedSetMargin = useDebouncedCallback(setMargin, DEBOUNCE_TIME);
+
+  const resetPosition = useCallback(() => {
+    if (stickyRef.current) {
+      stickyRef.current.style.marginTop = '0px';
+      stickyRef.current.classList.remove(TRANSITION_CLASS);
+    }
+
+    if (stickyOffsetRef.current > 0) {
+      stickyOffsetRef.current = 0;
+    }
+  }, []);
+
+  const handleScroll = useCallback(() => {
+    // put the sticky element back to default position
+    resetPosition();
+
+    // When the keyboard gets closed, both the 'scroll' and 'blur' events are fired.
+    // 'scroll' => 'blur' or 'blur' => 'scroll'
+    // We skip handling here when 'scroll' is fired after 'blur'.
+    // Otherwise, wrapper.getBoundingClientRect().top might return incorrect value
+    // due to keyboard closing animation.
+    // This would set wrong marginTop with gap above the sticky element.
+    if (blurred.current) {
+      blurred.current = false;
+      return;
+    }
+    // show the sticky element with delay
+    debouncedSetMargin();
+  }, [debouncedSetMargin, resetPosition]);
+
+  useEffect(() => {
+    window.addEventListener('scroll', handleScroll);
+    return () => {
+      window.removeEventListener('scroll', handleScroll);
+    };
+  }, [handleScroll]);
+
+  const handleBlur = useCallback(() => {
+    blurred.current = true;
+    resetPosition();
+  }, [resetPosition]);
+
+  return { handleBlur, stickyRef, wrapperRef };
+}
diff --git a/ui/tailwind.config.ts b/ui/tailwind.config.ts
index 99552990..4ebc989b 100644
--- a/ui/tailwind.config.ts
+++ b/ui/tailwind.config.ts
@@ -6,6 +6,7 @@ const config: Config = {
     extend: {
       animation: {
         'slide-up': 'slide-up 0.3s ease-in-out both',
+        'slide-down': 'slide-down 0.3s ease-in-out both',
       },
       keyframes: {
         shimmer: {
@@ -17,6 +18,10 @@ const config: Config = {
           '0%': { transform: 'translateY(30%)', opacity: '0' },
           '100%': { transform: 'translateY(0)', opacity: '1' },
         },
+        'slide-down': {
+          '0%': { transform: 'translateY(-100%)', opacity: '0' },
+          '100%': { transform: 'translateY(0)', opacity: '1' },
+        },
       },
     },
   },